Low-height dual or multi-band antenna, in particular for motor vehicles

ABSTRACT

The invention relates to an improved, low-height dual or multi-band antenna comprising surface transmitters, whose size varies in accordance with the frequency band to be transmitted. Said antenna is configured from a smaller surface transmitter that is located on top of a larger surface transmitter. The antenna is characterised by the following improved features: the dual or multi-band antenna is essentially configured as a one-piece punched and bent metal part; as a one-piece component, said antenna consists of at least two surface transmitters, which are electrically connected via a short-circuit; and at least the lowest surface transmitter for transmission in a lower frequency band and/or at least a surface transmitters that is lower than the surface transmitter for transmission in the highest frequency band have transmitter wings lying adjacent to their transmitter surface. When the antenna is viewed from above, the respective surface transmitter for transmission in a higher frequency band lies between the wings of said lower frequency band transmitters.

The invention relates to a low-height, dual or multiband antenna, inparticular for motor vehicles, as claimed in the precharacterizingclause of claim 1.

The 900 MHz or the so-called 1800 MHz band is used for communicationpurposes, particularly in German and European mobile radio networks. Theso-called 1900 MHz band is used for transmission, particularly in theUSA. UMTS networks, which will be the next to appear, are designed touse the 2000 and 2100 MHz band ranges.

Low-height antennas are desirable in particular in the motor vehiclefield and are intended to have electrical characteristics which are asgood as possible, that is to say in particular a wide bandwidth, a goodomnidirectional characteristic and a compact physical form.

Dual-band flat antennas have already been proposed on this basis and arealso referred to, inter alia, as “stacked dual-frequency-microstripe”PIF antennas.

One such antenna which is known from the prior art has a flat antennaelement which is parallel to a metallic base surface or base plate andis short-circuited on one of its longitudinal faces to the metallic baseplate by means of a short circuit which runs at right angles to the flatantenna element and to the base plate. The length and width, and thesize, of the flat antenna element are, by way of example, matched to thelowest frequency to be transmitted, for example to the 900 MHz band.

A flat antenna element based on a comparable principle is constructed onthis basis, which is intended for transmission of a wider frequency bandrange, and is correspondingly physically smaller. It is seated with itslongitudinal and transverse extent, which are shorter overall, with afurther flat antenna element approximately centrally, in a plan view, onthe physically larger flat antenna element located underneath it, to beprecise likewise in a position parallel to it. On one of itslongitudinal faces, preferably on the same longitudinal face as the flatantenna element for the lowest frequency band range, it is connected viaa short circuit to the flat antenna element located underneath it. Theshort-circuiting element is preferably likewise once again aligned atright angles to the two flat antenna elements.

The feed is provided via a feed line which preferably runs at rightangles to the flat antenna elements and is routed such that it runsessentially at right angles upward as far as the lower face of thetopmost flat antenna element from a feed point, for example a matchingnetwork, in the area of the base plate, from which the feed point isisolated. For this purpose, an appropriate passage opening is providedin the flat antenna element located underneath it, in order to route thefeed line as far as the topmost flat antenna element.

Although antennas such as these have in fact been proven in practice,the object of the present invention is to provide an improved flatantenna element whose production and assembly are considerably simplerthan those for previous solutions. According to the invention, theobject is achieved by the features specified in claim 1. Advantageousrefinements of the invention are specified in the dependent claims.

The low-height dual or multiband antenna according to the invention isdistinguished by its major parts being formed from a complete, integralstamped and bent part.

In other words, at least two flat antenna elements for transmission intwo frequency bands as well as a short circuit which acts between themare produced and formed from a single stamped sheet-metal part.

In one preferred development of the invention, the corresponding shortcircuit for connection of the flat antenna element which is intended forthe lowest frequency band range (that is to say that flat antennaelement which is provided adjacent to the metallic base plate) is also acomponent of the entire integral stamped and bent part, that is to sayit is a common component with the integral flat antenna.

A further preferred embodiment even provides for the feed line, whichruns essentially at right angles to the flat antenna elements, likewiseto be in the form of a stamped and bent part, to be precise as a part ofthe entire stamped and bent part.

The entire design can be cascaded a number of times, so that not onlytwo but also at least three flat antenna elements are formed, which areof different sizes, are each arranged one above the other and runessentially parallel to one another, in order that the compact antennacan also transmit and receive, for example, as a multiband antenna inthree band ranges.

Finally, it has also been shown that the dual or multiband antenna mayhave flat antenna elements which are not necessarily in each case formedat different heights to one another but at the same height, with theshort circuit between two flat antenna elements in this case thenlikewise being arranged such that it runs at the same height level.

The flat antenna elements can essentially be provided with parallel andvertical cut edges and bending edges in a plan view. However, it is justas possible for the stamped edges, which in each case point outwards, ofthe higher flat elements for transmission in the higher frequency bandrange to be designed, for example, such that they run diverging slightlyoutwards from their short-circuit links toward their free end, or suchthat they converge inward, or to have obliquely running end edge areasin particular at their free end. The stamped edges of the lower-levelflat elements can likewise be designed such that they run obliquely, inwhich case the stamped edges on the outside and inside need notnecessarily run parallel.

Another preferred development of the invention furthermore makes itpossible to provide for the antenna vanes to be lengthened downwards bya further bend.

In addition, the short-circuit connections need not be formed over theentire width of the respective flat element, but may be shorter than theadjacent transverse extent of the respective flat element.

The invention will be explained in more detail in the following textwith reference to drawings in which, in detail:

FIG. 1: shows a first perspective view of a first dual-band antenna;

FIG. 2: shows another perspective illustration of the dual-band antennaillustrated in FIG. 1;

FIG. 3: shows a corresponding rearward side view of the flat antennaillustrated in FIGS. 1 and 2;

FIG. 4: shows a corresponding plan view of the flat antenna shown inFIGS. 1 to 3;

FIG. 5: shows a plan view of a metallic blank plate (metal sheet) onwhich the stamping and bending lines for production of an antenna inFIGS. 1 to 4 are shown;

FIG. 6: shows an exemplary embodiment of a corresponding flat antenna,modified from that shown in FIG. 1;

FIG. 7: shows a plan view of the exemplary embodiment shown in FIG. 6;

FIG. 8: shows a perspective illustration of another modified exemplaryembodiment of a flat antenna;

FIG. 9: shows a plan view of the illustration shown in FIG. 8;

FIG. 10: shows a perspective illustration of another modified exemplaryembodiment;

FIG. 11: shows a further exemplary embodiment of a dual-band antennawith antenna surfaces at the same height;

FIG. 12: shows a perspective illustration of a further exemplaryembodiment with antenna vanes which have been lengthened downwards;

FIG. 13: shows a rearward side view of the illustration shown in FIG.12;

FIG. 14: shows a perspective illustration of a further exemplaryembodiment of a triband antenna; and

FIG. 15: shows a side view of the exemplary embodiment shown in FIG. 14.

FIGS. 1 to 4 show a first exemplary embodiment of a low-height compactdual-band antenna according to the invention, which comprises two flatantenna elements 3 a and 3 b which are arranged parallel to one another.An antenna element such as this is normally provided with a largermetallic surface or base plate 7, that is to say it is connected to it,or a corresponding antenna is, for example, when used on a motorvehicle, fitted at an appropriate point on the sheet-metal bodywork ofthe vehicle, which is then used as the metallic opposing surface or basesurface.

The lower flat element or the lower flat antenna element 3 a is tunedfor transmission in a lower or low frequency band, for example in the900 MHz band range. The physically smaller flat antenna element 3 bwhich is constructed above this is, for example, tuned for transmissionin the region of the 1800 MHz band range.

The upper flat antenna element 3 b is connected on its narrower boundaryface or edge 9 b, which is located on the left in FIG. 1, via a shortcircuit 11 b to the physically larger flat antenna element 3 a locatedunderneath it, with the short circuit 11 b in the illustrated exemplaryembodiment having a width which corresponds to the width of the upperflat antenna element 3 b.

The lower flat antenna element 3 a is likewise equipped on its narrowerboundary face 9 a, which is located on the left, with a verticalshort-circuiting surface 11 a, via which an electrical connection isnormally produced to the electrical base surface or base plate 7 thathas been mentioned.

Finally, the upper and the lower flat antenna elements are each equippedsuch that a part of the respective flat antenna element comprises aclosed metal surface section 130 a or 130 b, to which two antenna vanes203 a and 203 b, respectively, which are offset in the transversedirection of the antenna element, are then connected on the respectiveopposite face to the short circuit 11 a or 11 b.

In the illustrated exemplary embodiment, the entire antenna that isshown in FIG. 1 is produced from a single stamped and bent part, withthe exception of the base plate 7. In this context, FIG. 5 shows ametallic blank metal sheet in which the corresponding stamping lines 19are shown by dashed-dotted lines, with the bending edge 20 being shownby a dotted line. The flat antenna element 3 b for the respective higherfrequency band range can then be positioned higher than and parallel tothe flat antenna element 3 a located underneath it by means of thestamping and cutting process and by subsequently bending along thebending edges 21′a and 21′b, as can be seen from FIGS. 3 a and 3 b. Thebending process in this case results in the short circuits 11 a and 11 bbeing positioned at right angles to the plane of the flat antennaelements.

The plan view of the blank sheet-metal part shown in FIG. 5 in this caseshows that, in this exemplary embodiment, only the material areaidentified by x need be cut out and removed during the stamping process.The remaining parts are just stamped and/or folded and bent on thecorresponding lines in order then to produce the dual-band antennaillustrated in FIGS. 1 to 4.

Finally, a feed line 25 is also required, which is preferably providedat right angles to the plane of the flat antenna elements and is routedfrom underneath up to the lower face of the flat antenna element 3 babove it. In the illustrated exemplary embodiment, this feed line 25 islikewise produced as a stamped and bent part, for which purpose theuppermost flat antenna element 3 b has a recess 27 in the form of aslot, to be precise extending from a bending edge 29 which is formed atthe left of the end of the recess 27 which is in the form of a slot,thus making it possible to bend a narrow metal strip at right anglesdownward in order to form the feed line 25 that has been mentioned.

In the exemplary embodiment shown in FIGS. 1 to 4, the blank material,which is in the form of a plate, is thus used virtually completely,since the flat antenna element which is located between the outer sideedges 31 of the upper flat antenna element 3 b and the inner side edges33 of the flat antenna element located underneath it is formed just bymeans of a stamping or cutting line 19 without having to cut out thematerial. In the exemplary embodiment shown in FIGS. 6 and 7, incontrast, a respective short circuit 11 a or 11 b is made narrower inthe transverse direction of the flat antenna elements, so thatcorresponding material areas have to be stamped out of a blank metalplate while carrying out the stamping and bending process.

Furthermore, the front ends of the antenna vanes 203 a and 203 b are notprovided at their free end with end or cut edges 35 which run at rightangles to the longitudinal extent of the antenna vanes, but with end orcut edges 35 which run toward one another obliquely from the outsideinward, that is to say they converge.

In the exemplary embodiment shown in FIGS. 8 and 9, the outer cut edges31 of the respective higher flat antenna element converge from theshort-circuit face toward the free end, and in this case are parallel tothe correspondingly converging inner cut edges 33 of the lower flatantenna element 3 a. This results in antenna vanes 203 b which run to apoint, at least for the higher flat antenna element 3 b. The antennavanes 203 a of the lower flat antenna element have a width and extentwhich increase towards their free end. The outer end or cut edge canlikewise be designed such that it converges again, in which case thefront end tips of the antenna vanes 203 a of the lower flat antennaelement can then touch one another, or virtually touch one another.

In the exemplary embodiment shown in FIG. 10, the piece of feed line,which is likewise produced as a stamped or bent part, is likewise formedfrom the top downwards as an increasingly narrower metal strip, that isto say as a metal strip with stamped edges 39 which run toward oneanother, converge and are on opposite sides. Conversely, the shortcircuit 11 a has a trapezoidal shape running from the bottom upwards, atleast with respect to the flat antenna element for the lower frequencyband range. Finally, the exemplary embodiment illustrated in FIG. 11shows that the antenna surfaces as well as the antenna vanes for thevarious frequency band ranges may also be arranged at the same heightlevel, that is to say arranged in an O-shape or in the form of a fork,so that, in this exemplary embodiment as well, the short circuit 11 bwhich connects the two flat antenna elements 11 b and 11 a is located inan arrangement at the same height.

A multiband antenna can also be designed in a corresponding manner tothe explained exemplary embodiment, specifically by adding a third flatantenna element, for example, to the corresponding cascading of the twoflat antenna elements as explained in the drawings, which third flatantenna element is physically smaller and is formed in a correspondingrepetitive manner on the second flat antenna element. In this case aswell, the complete antenna formed in this way may be produced as asingle stamped and bent part, that is to say it may be integral.

The following text refers to the exemplary embodiment shown in FIGS. 12and 13. In this exemplary embodiment, the antenna element vanes 203 a ofthe lowermost flat antenna element are provided with antenna vanesections 203 a′ which have been lengthened downwards, thus resulting inthe advantage that the antenna vanes 203 a can be shortened overall incomparison to other exemplary embodiments and, at the same time, aremechanically more robust. In the illustrated exemplary embodiment, thecorresponding antenna vane sections 203 a′ are in this case formed withbent metal sections, which project vertically downward, on the outeredge of the antenna vanes.

If specified appropriately, antenna vane sections such as these may alsoalternatively or additionally be provided on an antenna vane 203 b on aflat antenna element 3 b for transmission in a higher frequency band.

FIGS. 14 and 15 illustrate a corresponding antenna type, which issuitable for transmission and reception in three bands which are offsetwith respect to one another. The corresponding design of the flatantenna element 3 b in this exemplary embodiment is effectively cascadedonce again, in comparison to the previous exemplary embodiments, by theaddition of a physically smaller flat antenna element 3 c located aboveit, which likewise once again has corresponding antenna element vanes303 a. The connection to the antenna element 3 b located underneath itis likewise made via a corresponding short circuit 11 c. The feed isprovided via a feed line 25, which leads to the uppermost flat antennaelement 3 c.

The antennas which have been explained are so-called PIF antennas, thatis to say so-called “planar inverted F antennas”. In this case, it isknown that the characteristics of the respective antenna can beinfluenced in the case of antennas such as these by the configurationand the location of the feed point and of the short circuits. Thecharacteristics of the antennas can thus be individually matched to theinfluences of the respective vehicle bodywork and the respectiveinstallation location by the configuration and the location of the feedpoint and of the short circuits. In this case, the short circuits, forexample the short circuits 11 a and 11 b, are generally each located onthe narrow face of the antenna arrangement, which is preferablybasically longitudinally symmetrical (that is to say symmetrical withrespect to a vertical central longitudinal plane). The feed point forthe antenna is preferably provided on this longitudinal line of symmetryor longitudinal plane of symmetry of the antenna. The antenna impedance,which should normally be 50 Ohms for car radio antennas, can also bematched by the position of the feed point and its distance from theshort circuit.

1. A low-height dual or multiband antenna comprising: a) the dual ormultiband antenna is arranged or can be positioned on a metallic basesurface or base plate, b) the dual or multiband antenna has at least twoflat antenna elements for operation in two frequency bands which areoffset with respect to one another, c) the two flat antenna elements arealigned parallel, or at least approximately parallel, to one another, d)the size of the at least two flat antenna elements decreases from thatflat antenna element which is closest to the base surface to that flatantenna element which is furthest away from the base surface or baseplate, e) the flat antenna element is in each case connected to the flatantenna element for transmission in a higher frequency band range, andthe flat antenna element is intended for transmission in a frequencyband range which is lower than this, f) the flat antenna elements have ashort circuit on one face, such that one flat antenna element fortransmission in a higher frequency band is short-circuited via the shortcircuit to the flat antenna element for transmission in a lowerfrequency band than this, and the flat antenna element for transmissionin the lowest frequency band range is connected or can be connected viaa short circuit (ha) to the metallic base surface or base plate,including the following further features: g) the dual or multibandantenna is in the form of an integral stamped and bent metal part, h)the antenna has, as an integral component, at least two flat antennaelements and the short circuit which is provided between two flatantenna elements, i) at least the flat antenna element for transmissionin the lowest frequency band and/or for transmission in a frequency bandwhich is lower than an upper frequency band has or have adjacent to itsor their antenna element surface antenna element vanes which areelectrically connected to the associated antenna element surfaces, withthe respective flat antenna element for transmission in a frequency bandhigher than this coming to rest between these antenna element vanes in aplan view of the antenna, j) the flat antenna element for transmissionin a higher frequency band is arranged on the same plane as the flatantenna elements for transmission in a frequency band lower than this,or is arranged with a lateral offset with respect to it on a plane whichruns parallel or at least approximately parallel to it, and k) a feedline which runs from underneath to the lower face of the flat antennaelement arranged at the top is likewise in the form of a stamped andbent part, which is integrally connected to the remaining parts of theantenna formed in this way.
 2. The antenna as claimed in claim 1,wherein the electrical short circuit (jib) which connects the adjacentflat antenna elements is connected to the two flat antenna elements viatwo bending edges in opposite senses.
 3. The antenna as claimed in claim1, wherein the flat antenna element which is arranged at the bottom isprovided with a short circuit (ha) which forms a part of the antenna andis connected via a bending line to the antenna element surfaces of theflat antenna element.
 4. The antenna as claimed in claim 1, wherein arecess which is in the form of a slot is incorporated in the flatantenna element arranged at the top, to be precise forming a feed line,which is curved downward over a bending line, essentially at rightangles to the plane of the flat antenna element.
 5. The antenna asclaimed in claim 1, wherein the end edges of the antenna vanes run atright angles to the longitudinal edges of the antenna vane.
 6. Theantenna as claimed in claim 1, wherein the end edges of the antennavanes are aligned such that they converge from the outer edges towardthe center or diverge outwards from the outer edges.
 7. The antenna asclaimed in claim 1, wherein those side edges which point outward of theantenna vanes (203 b) of the antenna elements for higher frequencies runfrom their face which is provided with a short circuit such that theyconverge toward their free end or diverge outwards.
 8. The antenna asclaimed in claim 1, wherein those stamped edges which point inward ofthe antenna vanes of the antenna elements which are provided for thelower transmission ranges run from their short-circuit face such thatthey converge toward their free end or diverge outward.
 9. The antennaas claimed in claim 1, wherein the short circuits have a rectangularshape and preferably extend over the entire width of the associatedantenna element.
 10. The antenna as claimed in claim 1, wherein theshort circuits are shorter than the width of the antenna elements. 11.The antenna as claimed in claim 10, wherein the short circuits have atriangular or trapezoidal shape.
 12. The antenna as claimed in claim 1,wherein the antenna vanes of the flat antenna elements are arranged atdifferent height levels, with in each case one flat antenna element fortransmission in a higher frequency band range being arranged above onefor transmission in a frequency band range which is lower than this. 13.The antenna as claimed in claim 1, wherein at least two flat antennaelements are arranged with their antenna vanes at the same height level.14. The antenna as claimed in claim 1, wherein the antenna element vanesare preferably provided on their boundary edge which points outward withantenna vane sections which are preferably aligned such that they pointdownward.
 15. The antenna as claimed in claim 1, wherein the antenna isin the form of a triband antenna and, cascaded with respect to it, has athird flat antenna element which has at least a similar shape to that ofthe other two flat antenna elements and is matched for transmission inthe highest frequency band range.